The present invention relates generally to a method and apparatus for the unattended weighing of filters used for sampling air quality. More particularly, the present invention relates to a method of and apparatus for the unattended weighing of respirable particulate matter (RSP) filters used for air quality sampling.
Various government agencies, for example, the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) in the United States have become increasingly interested and concerned about indoor air quality. In the future, it is likely that standards will be promulgated by those or other governmental agencies regarding indoor air quality. Already, certain business enterprises are subject to indoor air quality standards.
Indoor air quality studies are generally conducted utilizing a filter and a pump which draws air through the filter. Alternatively, the filters can be used together with a holder but without a pump. By being placed in an indoor environment, the filters gather respirable particulate matter or other particulates which then must be weighed in order to determine the percentage of such particulate matter within the indoor air and, therefore, the quality of the indoor air being measured.
The RSP matter determinations are made in microgram quantities whereas most air quality control studies are now conducted in milligram quantities. Thus, due to the greater accuracy required with RSP determinations, the RSP filter weighing procedure is a time consuming and tedious task. The current process, which is performed manually, requires eight to ten minutes for each weighing. Due to a typical sample load of, for example, 6,000 weighings per year, the time required and the tediousness of the task require extensive outlays for personnel and limit the number of samples which can be weighed in a given time. Further, since it is anticipated that indoor air quality standards will be imposed in the future, the sample load of filters to be weighed will be increased significantly.